1. Field of the Invention
The present invention relates to a keyboard device suitable for use in an input/output device of a word processor, a personal computer or the like.
2. Description of the Related Art
As shown in FIGS. 5 through 7, in a conventional keyboard device used in such an input/output device, a switch board 52 consisting of a flexible insulating material provided with a circuit (not shown) is placed on an insulating board 50 provided with a conductor (not shown) through the intermediation of a plate-like spacer 51 consisting of an insulating material having a hole 51a to thereby form a switch section.
A support member 53, which is formed of synthetic resin, is equipped with two holding sections 53a having a hole, two engagement sections 53c having a slide groove 53b, and a hole portion 53d provided between the holding sections 53a and the engagement sections 53c. These members constitute one set, and a plurality of such sets are formed. This support member 53 is placed on the switch board 52.
A substantially H-shaped first lever section 54, which is formed of synthetic resin, has at its ends pairs of arms 54c and 54d having round protrusions 54a and 54b at their ends. In the central portion of the first lever, there are provided outwardly protruding shaft members 54e. The protrusions 54b, which are engaged with the engagement section 53c of the support members 53, are slidable within the slide grooves 53b and on the support member 53.
Each one of pair of second lever sections 55 has at its ends round protrusions 55a and 55b, and a recess 55c provided between the protrusions 55a and 55b. The protrusions 55a are fitted into the holes of the holding sections 53a. Further, the shaft members 54e of the first lever section 54 are fitted into the recesses 55c. The first and second levers 54 and 55 cross each other and combined so as to be rotatable.
A key top 56, which is formed of synthetic resin, has on the back side two holding sections 56a each having a hole and two engagement sections 56c each having a slide groove 56b. The protrusions 54a of the first lever section 54 are rotatably supported by the holding sections 56a. Further, the protrusions 55b of the second lever sections 55 are slidably held by the engagement sections 56c, whereby the key top 56 is mounted on the first and second lever sections 54 and 55.
A dome-like elastic member 57 consisting of insulating rubber is positioned inside the hole portion 53d of the support member 53 and, in this condition, placed on the switch board 52, with the forward end of the elastic member 57 abutting the back side of the key top 57.
A plurality of first and second lever sections 54 and 55, a plurality of key tops 56 mounted on these lever sections 54 and 55, and a plurality of elastic members 57, described above, are arranged on the switch section in a plurality of rows.
In this keyboard device, constructed as described above, when the key top 56 is depressed, the protrusions 54a and 55a of the first and second lever sections 54 and 55 rotate within the holding sections 53a and 56a, and the protrusions 54b and 55b slide within the slide grooves 53b and 56b. With the above rotation and sliding, the first and second lever sections 54 and 55 move downwards and, at the same time, the key top 56 also moves downwards. When the elastic member 57 is depressed by the key top 56 and the dome-like elastic member 57 is thereby deformed to flip over, the switch board 52 is depressed by the elastic member 57, and a circuit contact on the switch board 52 is brought into contact with the conductor on the insulating board 50, whereby the switch is turned ON.
After this, the depression of the key top 56 is cancelled, and the first and second lever sections 54 and 55 and the key top 56 are restored to the state before the depression due to the elasticity of the elastic member 57, and, at the same time, the switch board 52, which has been depressed by the elastic member 57, is restored to the former state due to its restoring capacity, and brought out of contact with the insulating board 50, whereby the switch is turned OFF.
The depression of the key top 56 by the operator is not uniform. When end portions (the upper and lower end portions in FIG. 6) of the key top 56 is depressed, the fork-like arm portions 54d and the protrusions 54b provided at the end thereof, which has a low level of strength, are deflected to a large extent, as shown in FIG. 7, and greatly inclined to positions Y and Z indicated by the dot lines. This great inclination leads to an inclination of the key top 56, thereby greatly affecting the operability.
In the conventional keyboard device, the arm portions 54d of the first lever portion 54 are formed in a fork-like configuration, and protrusions 54b are provided at the forward end thereof to engage engagement sections 53c, so that the arm portions 54d and the protrusions 54b are rather weak, and when an end portion of the key top 56 is depressed, the key top 56 is greatly deflected and inclined to a large degree, resulting in a poor operability. In addition, due to this great inclination, the protrusions 54b cannot slide smoothly in the slide grooves 53b, resulting in a poor operability.
Further, since the protrusions 54b of the first lever section 54 are mounted on the support member 53, which means their height is rather large due to the thickness of the support member 53, resulting in a problem in terms of thickness.